Technological developments have significantly increased the demand for more reliable and versatile detection and measuring equipment. The detection and measurement of sulfur and sulfur bearing constituents are a prime concern for both technological and environmental reasons. A suitable device should give a specific, clear response to, and a rapid recovery from, all the volatile sulfur compounds in the gas sample. The device should further minimize interference from other constituents such as hydrocarbons. Measurements from the low ppm, (parts per million) range to a high pph (parts per hundred) range should be well within the detector's capabilities. The device should possess a low noise level, operational stability and sulfur response repeatability.
A special problem is presented by sour natural gas which may contain large amounts of hydrogen sulfide and comparatively smaller amounts of other sulfur bearing compounds such as carbonyl sulfide and lighter mercaptans. Generally, determination of the dilute components is frustrated because of the higher concentration contaminants, ultimately giving an unreliable analysis.
One commercially available unit is a phosphorus and sulfur specific flame photometric detector for use with a gas chromatograph. The device comprises a burner, a mirror and optical filters for the sulfur and phosphorous components, ignition plugs and a photomultiplier tube for each of the optical filtering devices. The device is characterized by alignment of the photomultiplier optical axis and survey area with the uppermost portion of the burner flame. Such positioning increases the sensing element's sensitivity to hydrocarbon presence and interferes with a clear reading specific to the sulfur and/or phosphorous content. Furthermore, the device has a limited operational range of from approximately 5 ppb (parts per billion) to 5 ppm (parts per million). "Sulfur saturation" severely limits the unit's reliable operational range and makes the apparatus undesirable for sour gas analysis.